Method for manufacturing semiconductor dynamic quantity sensor

• US 6,287,885 B1
• Filed: 05/06/1999
• Issued: 09/11/2001
• Est. Priority Date: 05/08/1998
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yamamoto, Toshio, Ozoe, Shoji, Kanosue, Masakazu, Fujino, Seiji, Asami, Kazushi, Sakai, Minekazu, Fukada, Tsuyoshi, Muto, Hiroshi, Takeuchi, Yukihiro, Yoshihara, Shinji, Aoyama, Seiki, Murata, Minoru, Terada, Masakazu, Sugito, Hiroshige
• Primary Examiner(s): Mulpuri, Savitri
• Application Number:
  US09/306,381
• Time in Patent Office: 859 Days
• Field of Search: 438/48, 438/50, 438/51, 438/52, 438/53, 438/700, 438/701, 438/706, 438/719, 438/723, 257/415, 257/417, 257/418, 216/2, 735/141.6, 735/143.3, 735/143.4, 73/78, 737/24
• US Class Current: 438/48
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 2203/033 Trenches
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 1/00936 Releasing the movable structure without liquid etchant
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: B81C 2201/053 Depositing a protective layers
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

In a method for manufacturing a semiconductor acceleration sensor, a movable portion including a mass portion and movable electrodes is formed in a single crystal silicon thin film provided on a silicon wafer through an insulation film by etching both the single crystal silicon thin film and the silicon wafer. In this case, the movable portion is finally defined at a movable portion defining step that is carried out in a vapor phase atmosphere. Accordingly, the movable portion is prevented from sticking to other regions due to etchant during the manufacture thereof.

Claims

1. A method for manufacturing a semiconductor dynamic quantity sensor, comprising steps of:

preparing a semiconductor substrate including a first semiconductor region and a second semiconductor region isolated from the first semiconductor region by an insulation film interposed therebetween; and

forming a movable portion in the first semiconductor region by etching both the first semiconductor region and the second semiconductor region,

wherein the movable portion is defined finally at a movable portion defining step that is carried out in a vapor phase atmosphere in the step of forming the movable portion,

wherein the step of forming the movable portion includes steps of;

forming a trench in the first semiconductor region;

etching the second semiconductor region to expose at least a portion of the insulation film corresponding to the trench; and

performing the movable portion defining step in the vapor phase atmosphere,

wherein the portion of the insulation film is removed at the movable portion defining step so that the movable portion and a fixed portion fixed to the substrate and facing the movable portion are defined.

2. The method as recited in claim 1, wherein one of the first semiconductor region, the second semiconductor region, and the insulation film is etched at the movable portion defining step to finally define the movable portion.

3. The method as recited in claim 1, wherein the step of forming the movable portion includes:

a step of forming a protection film on the first semiconductor region and in the trench after forming the trench;

a step of etching the insulation film after etching the second semiconductor region; and

the movable portion defining step for etching the protection film.

4. The method as recited in claim 1, wherein:

the trench is formed in the first semiconductor region to remain part of the first semiconductor region at a bottom thereof; and

the part of the first semiconductor region at the bottom of the trench is removed at the movable portion defining step.

5. The method as recited in claim 1, further comprising a step of forming a protection film on the first semiconductor region and in the trench, wherein;

the trench is formed in the first semiconductor region to remain part of the first semiconductor region at the bottom thereof; and

the protection film is removed at the movable portion defining step after removing the part of the first semiconductor region.

6. The method as recited in claim 1, wherein:

the step of etching the second semiconductor region includes a first etching step of etching the second semiconductor region to remain part of the second semiconductor region on the insulation film with a specific thickness, and a second etching step of etching the part of the second semiconductor region remaining on the insulation film in a vapor phase atmosphere to expose the insulation film; and

the insulation film is removed at the movable portion defining step to form an opening communicating with the trench.

7. The method as recited in claim 6, wherein:

the second semiconductor region has an impurity high concentration layer including impurities therein and contacting the insulation film with a specific depth; and

the first etching step is performed using a specific etchant to be substantially stopped when the impurity high concentration layer is exposed, in accordance with an etching rate of the specific etchant to the impurity high concentration layer.

8. The method as recited in claim 6, wherein:

the first etching step is performed using a specific etchant in a state where a voltage is applied to the first semiconductor region to form a depletion layer in a portion of the second semiconductor region contacting the insulation film; and

the first etching step is substantially stopped when the depletion layer is exposed.

9. The method as recited in claim 1, wherein the second etching step of etching the part of the second semiconductor region and the movable portion defining step are successively performed at an equal etching condition with each other.

10. The method as recited in claim 1, wherein the first etching step is an anisotropic etching step.

11. The method as recited in claim 1, wherein:

the step of etching the second semiconductor region is carried out in a vapor phase atmosphere; and

the insulation film is removed at the movable portion defining step.

12. The method as recited in claim 11, wherein the step of etching the second semiconductor region is an anisotropic dry etching step.

13. The method as recited in claim 11, wherein the step of etching the second semiconductor region and the movable portion defining step are successively carried out at an equal etching condition with each other.

14. The method as recited in claim 1, wherein the step of forming the trench includes steps of:

forming a mask on the first semiconductor region;

performing an etching to the first semiconductor region to form a first trench portion and a second trench portion through the mask, the first trench portion having a width larger than that of the second trench portion; and

stopping the etching when the insulation film is exposed from the first trench portion and the first semiconductor region remains at a bottom of the second trench portion, and

wherein the first semiconductor region remaining at the bottom of the second trench portion is removed at the movable portion defining step in the vapor phase atmosphere after removing the insulation film.

15. The method as recited in claim 14, wherein the first trench portion and the second trench portion are formed by an anisotropic dry etching.

16. The method as recited in claim 1, further comprising a step of covering the first semiconductor region with a protection film after forming the trench, the protection film being made of a material separatable from the first semiconductor region.

17. The method as recited in claim 1, further comprising a step of adjusting a shape of the movable portion after the movable portion is finally defined by the movable portion defining step.

18. The method as recited in claim 17, wherein:

the trench is formed by a dry etching; and

the step of adjusting the shape of the movable portion is an auxiliary dry etching step that is carried out to the movable portion from a second semiconductor region side.

19. The method as recited in claim 18, wherein the auxiliary dry etching step is an isotropic dry etching step.

20. The method as recited in claim 1, wherein the semiconductor substrate is cut into a sensor chip by a dicing step before performing the movable portion defining step.

21. The method as recited in claim 1, wherein the step of forming the movable portion in the first semiconductor region includes a step of polishing the second semiconductor region to have a specific thickness.

22. The method as recited in claim 1, further comprising a step of forming a hydrophobic thin film on the movable portion after the movable portion defining step, wherein the step of forming the hydrophobic thin film is carried out simultaneously with the moveable portion defining step in the vapor phase atmosphere.

23. The method as recited in claim 21, wherein the step of forming the hydrophobic thin film is carried out by a reactive ion etching (RIE) in plasma.

24. The method as recited in claim 21, wherein a contact angle of the hydrophobic thin film with water is equal to or larger than 70 degrees.

25. The method as recited in claim 21, wherein the hydrophobic thin film is made of an organic material.

26. The method as recited in claim 21, wherein the hydrophobic thin film is a fluorine type thin film including fluorine.

27. The method as recited in claim 21, wherein the movable portion defining step and the step of forming the hydrophobic thin film are successively carried out in a chamber under first and second etching conditions, respectively.

28. The method as recited in claim 1, wherein the movable portion defining step is a reactive ion etching step carried out in plasma between a first electrode and a second electrode facing each other for etching the insulation film, the reactive ion etching step being carried out in a state where;

the semiconductor substrate is disposed on the first electrode with the insulation film having an exposed surface facing the second electrode and with an intermediate member interposed between the semiconductor substrate and the first electrode, the intermediate member preventing a surface of the semiconductor substrate corresponding to the exposed surface of the insulation film on an opposite side of the insulation film from contacting the first electrode.

29. The method as recited in claim 28, wherein the intermediate member is conductive.

30. The method as recited in claim 28, wherein the intermediate member includes a conductive layer and a silicon oxide layer.

31. The method as recited in claim 30, wherein the conductive layer is made of silicon.

32. The method as recited in claim 3, wherein:

the trench includes a plurality of trenches for forming a plurality of movable electrodes and a plurality of fixed electrodes facing each other; and

the protection film fills the plurality of trenches as gaps that are provided between the plurality of movable electrodes and the plurality of fixed electrodes, respectively.

33. The method as recited in claim 5, wherein:

the trench includes a plurality of trenches for forming a plurality of movable electrodes and a plurality of fixed electrodes facing each other; and

the protection film fills the plurality of trenches as gaps that are provided between the plurality of movable electrodes and the plurality of fixed electrodes, respectively.

34. The method as recited in claim 4, wherein:

the trench includes a plurality of trenches for forming a plurality of movable electrodes and a plurality of fixed electrodes; and

the part of the first semiconductor region that is left by forming the plurality of trenches in the first semiconductor region is removed at the movable portion defining step to make the plurality of movable electrodes movable with respect to the plurality of fixed electrodes.

35. The method as recited in claim 5, wherein:

the trench includes a plurality of trenches for forming a plurality of movable electrodes and a plurality of fixed electrodes; and

the part of the first semiconductor region that is left by forming the plurality of trenches in the first semiconductor region is removed at the movable portion defining step to make the plurality of movable electrodes movable with respect to the plurality of fixed electrodes.

36. The method as recited in claim 22, wherein the vapor phase atmosphere at the movable portion defining step contains gas for forming the hydrophobic thin film.

37. A method for manufacturing a semiconductor dynamic quantity sensor, comprising:

preparing a semiconductor substrate composed of a first semiconductor region, a second semiconductor region, and an insulation film interposed between the first semiconductor region and the second semiconductor region;

forming a first trench in the first semiconductor region from a first surface of the semiconductor substrate;

forming a second trench in the second semiconductor region from a second surface of the semiconductor substrate at an opposite side of the first trench, at a position corresponding to the first trench so that at least one of the insulation film, a part of the first semiconductor region, and a part of the second semiconductor region remains between a bottom of the first trench and a bottom of the second trench as a remaining portion; and

dry-etching the remaining portion in a vapor phase atmosphere to make the first trench communicate with the second trench by removing a portion of the insulation film.

38. The method as recited in claim 37, wherein a movable portion of the sensor is formed by forming the first trench and the second trench in the semiconductor substrate, and is finally released by dry-etching the remaining portion.